Randy did not want to fight in the rumble because he was tired of the fighting and did not hold Bob’s death against Ponyboy.
Ponyboy is upset that Johnny is being charged with murder, even though the Socs that were with Bob admit that they were the ones who attacked Johnny and Ponyboy.
His buddy Randy Adderson, who had helped jump us, also said it was their fault and that we'd only fought back in self-defense. (ch 7, p. 180)
Ponyboy says he hates Randy, because he associates him with Bob and the Socs. Pony blames them for Bob’s death, their needing to run, and Johnny’s injuries. Yet when Randy asks to talk to him, he goes.
Randy says he is not going to show at the rumble between the greasers and Socs.
"I'm sick of all this. Sick and tired. Bob was a good guy. He was the best buddy a guy ever had. I mean, he was a good fighter and tuff and everything, but he was a real person too. You dig?" (ch 7, p. 117)
Randy notes that Bob is dead, and there is nothing that can bring him back. He was just a spoiled rich kid, and enough people have been hurt. He sees no need for revenge.
Randy is expressing feelings that many of them feel. The cycle of violene keeps perpetuating itself, as they each try to avenge their friends' deaths. They are all sick of it, but they are all in pain. Not everyone has the strength Randy has.